Ophthalmic and contact lens solutions using carnitine

ABSTRACT

The present invention relates to a lens care solution having 0.001 to about 5 weight percent of a low molecular weight amine of the general formula: 
     
       
         
         
             
             
         
       
     
     where R 1 , R 2 , R 3  and R 4  are —H or low molecular weight radicals, and R 5  is a low molecular weight radical, or salt thereof; an effective amount of a tonicity agent; and the balance water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and is a divisional of U.S. Ser. No.14/843,066 (filed Sep. 2, 2015) which is a divisional of U.S. Ser. No.13/870,094 (filed Apr. 25, 2013, now U.S. Pat. No. 9,149,555) which is adivisional of U.S. Ser. No. 13/195,389 (filed Aug. 1, 2011, nowabandoned) which is a continuation of U.S. Ser. No. 10/294,509 (filedNov. 14, 2002, now U.S. Pat. No. 8,557,868) which is a continuationapplication of U.S. Ser. No. 09/706,317 (filed Nov. 4, 2000, nowabandoned). The content of each of the aforementioned patentapplications is hereby incorporated by reference.

STATEMENT REGARDING FEDERALLY FUNDED RESEARCH OR DEVELOPMENT

This invention was made with support from a government grant under grantnumber EY11572 from the National Institute of Health. The government hasretained certain rights in this invention.

SUMMARY OF THE INVENTION

The present invention relates to contact lens care solutions that haveimproved ability to resist protein deposition and to provide lensestreated with such solutions to stabilize proteins more effectively, andto decrease the degree of other cationic depositions on said lenses,such as cationic preservative deposition of the lenses. The solutions ofthe present invention employ short chain quaternary amines as anadditive to state of the solutions in order to decrease the denaturationof proteins during cleaning cycles and to coat treated lenses todecrease the number of active binding sites on the lenses. The sortchain quaternary amines are of the general chemical formula:

where R₁₋₅ generally is a short chain of I to 4 carbon atoms withhydroxyl or carboxylic acid functionality or a salt thereof. Inparticular R₁₋₅ may be chosen to be carnitine, betaine, or choline orsalts thereof. These cationic amines also provide increased preservativeefficacy, reduce the potential for irritation by decreasing thepossibility of cationic preservative binding on lenses, and furthermoreact as buffering agents to provide increased pH stability for preparedsolutions. Specifically R₁, R₂, R₃ and R₄ are —H or from the group ofradicals below, or salts thereof, and R₅ is chosen from the group ofradicals below, or salts thereof:

Specifically compounds that meet the requirements of the presentinvention as an amine include, but are not limited to Betaine; Bicine(N,N-Bis(2-hydroxyethyl)-glycline); Bis-Tris(Bis-(2-hydroxyethyl)imino-tns (hydroxymethyl) methane; Choline;Carnitine; Creatine; Creatinine; Diisopropylamine; Diethanolamine;dimethyl Aspartic Acid; Dimethyl glutamate; Methyl Aspartate;Methylethanolamine; Hydroxymethyl Glycinate; Triethylamine;Triethanolamine; Tricine(N-tris(hydroxymethyl)methyl glycine); andTriisopropanolamine, and the like.

Protein binds to contact lens and form tenacious deposits that must beremoved by mechanical rubbing or enzymatic hydrolysis. Physiologicproblems associated with antigenic response to the denatured protein.Adversely affects optical clarity. Since denatured proteins arehydrophobic, heavily deposited lenses will feel dry and uncomfortable.Therefore, systems that are able to reduce protein adsorption willresult in improved quality of wear for the individual.

It is thought that contact lens have a net negative charge. Cationicprotein will preferentially bind to these lenses. The low molecularweight amines will compete for the bind sites and reduce the amount ofprotein that is deposited. The strength of competition is based on thebinding strength of the competing amine. Quaternary amines arerecognized as strong binding groups whose charge is independent of pH.Progressive substitution of the quaternary group is acceptable providingthe pH is controlled to ensure an cationic charge. Removing more thanthree of the substituents will result in a primary amine which has thepotential for binding to reducing sugars such as glucose and form acolored Schiff Base reaction product. Therefore, the preferred compoundsare secondary, tertiary, and quaternary low molecular weight amines withat least one hydrophilic substituent.

Methods of Use

The solution of the present invention are may be used in several modes:preferably, the solutions are used to pre-treat the lens with the lowmolecular weight (LMW) amines prior to insertion. These LMW amines areadded to the isotonic aqueous lens vial solution. The solution may bebuffered or the amines may act as their own buffer to control the pH.The solution should be isotonic (150-450 mOsm) in order to ensure thefull lens matrix is properly hydrated and the sites are available forbinding. The pH should be approximately neutral (4.5 to 8.5). This willensure the lenses that rely on carboxylic acids for lens hydration arefully ionized at a pH above 4.5. The amines are cationic at a pH below8.5 and therefore function well to prevent protein deposition atphysiological pH ranges.

The solutions may also be used to repetitively treat contact lenses withthe LMW amines to replenish any material that may have dissociated fromthe lens during wear. In this case, since the solution is generallypreserved with a cationic preservative, these amines will compete withthe cationic preservative for binding to the lens, and provide furtheradvantages in reducing contact lens discomfort.

Lastly the solutions may be applied directly to lenses while on the eyeto replenish any material that has dissociated from the lens duringwear.

Formulations

The present invention comprises 0.0001 to 5 weight percent of shortchain quaternary amines (the LMW amines described above) and a secondcontact lens solution agent. These agents may include but are notlimited to an effective amount of a preservative component, for example,an effective preserving amount of a non-oxidative antimicrobialcomponent. Any suitable preservative component may be employed providedthat it functions as a preservative and has no significant detrimentaleffect on the contact lens being treated or the wearer of the treatedcontact lens. Examples of useful preservative components include, butare not limited to, poly[dimethylimino-2-butene-1,4-diyl] chloride,alpha [4-tris (2-hydroethyl) ammonium-dichloride (available from OnyxCorporation under the trademark Polyquarternium I Registered TM),benzalkonium halides such as benzalkonium chloride, alexidine salts,chlorhexidine salts, hexarnethylene biguanides and their polymers, andthe like and mixtures thereof.

The amount of preservative component included varies over a relativelywide range depending, for example, on the specific preservativecomponent being employed. Preferably, the amount of preservativecomponent is in the range of about 0.000001% to about 0.001% or more.

The liquid media, e.g., aqueous liquid media, employed preferablyinclude a buffer component which is present in an amount effective tomaintain the pH of the liquid medium in the desired range. This buffercomponent may be present in the liquid medium, e.g., either separatelyor in combination with one or more of the other presently usefulcomponents, e.g., with the hydrogen peroxide. Among the suitable buffercomponents or buffering agents which may be employed are those which areconventionally used in contact lens care products. Examples of usefulbuffer components include those with carbonate functionalities,bicarbonate functionalities, phosphate functionalities, boratefunctionalities, and amine functionalities the like and mixtures thereofThe buffers may be alkali metal and alkaline earth metal salts, inparticular sodium and potassium.

Further, in order to avoid possible eye irritation, it is preferred thatthe presently useful combined liquid medium has an osmolality (a measureof tonicity) of at least about 200 mOsmollkg, preferably in the range ofabout 200 to about 350 or abou 400 mOsmollkg. In an especially usefulembodiment, the osmolality or tonicity o the combined liquid mediumsubstantially corresponds to the tonicity of the fluids of the eye, inparticularly the human eye.

Any suitable ophthalmically acceptable tonicity component or componentsmay be employed, provided that such component or components arecompatible with the other ingredients of the combined liquid medium anddo not have deleterious or toxic properties which could harm the eye.Examples of useful tonicity components include sodium chloride,potassium chloride, mannitol, dextrose, glycerin, propylene glycol andmixtures thereof In one embodiment, the tonicity component is selectedfrom inorganic salts and mixtures thereof

The amount of ophthalmically acceptable tonicity component utilized canvary widely. In one embodiment, the tonicity component is preferablypresent in the combined liquid medium in an amount in the range of about0.5 to about 0.9% of the combined liquid medium.

One or more additional components can be included in one or more of thepresent useful liquid media. Such additional component or components arechosen to impart or provide at least one beneficial or desired propertyto the liquid media. Such additional components may be selected fromcomponents which are conventionally used in one or more contact lenscare compositions and which do not detrimentally interact with the othercomponents present. Examples of such additional components includecleaning agents, wetting agents, nutrient agents, sequestering agents,viscosity builders, contact lens conditioning agents, colorants, and thelike. These additional components may each be included in the combinedliquid medium in an amount effective to impart or provide the beneficialor desired property to the combined liquid medium. Such additionalcomponents may be included in the presently useful liquid media inamounts similar to the amounts of such components used in other, e.g.,conventional, contact lens care products.

Examples of useful sequestering agents include disodium ethylenediaminetetraacetate, alkali metal hexametaphosphate, citric acid, sodiumcitrate and mixtures thereof.

Examples of useful viscosity builders include hydroxyethyl cellulose,hydroxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol andmixtures thereof.

In a particularly useful embodiment further includes at least one enzymeeffective to remove debris or deposit material from a contact lens.Among the types of debris that form on contact lens during normal useare protein-based debris, mucin-based debris, lipid-based debris andcarbohydrate-based debris. One or more types of debris may be present ona single contact lens.

The enzyme employed may be selected from peroxide-active enzymes whichare conventionally employed in the enzymatic cleaning of contact lenses.For example, many of the enzymes disclosed in Huth et al U.S. ReissuePat. No. 32,672 and Karageozian et al U.S. Pat. No. 3,910,296 are usefulin the present invention. These patents are incorporated in theirentirety by reference herein. Among the useful enzymes are thoseselected from proteolytic enzymes, lipases and mixtures thereof.Preferred proteolytic enzymes are those which are substantially free ofsulfhydryl groups or disulfide bonds, whose presence may react with theactive oxygen in the HPLM to the detriment of the activity of theenzyme. Metallo-proteases, those enzymes which contain a divalent metalion such as calcium, magnesium or zinc bound to the protein, may also beused.

A more preferred group of proteolytic enzymes are the serine proteases,particularly those derived from Bacillus and Streptomyces bacteria andAspergillus molds. Within this grouping, the still more preferredenzymes are the derived alkaline proteases generically called subtilisinenzymes. Reference is made to Keay, L., Moser, P. W. and Wildi, B. S.,“Proteases of the Genus Bacillus”. II. Alkaline Proteases,“Biotechnology & Bioengineering”, Vol. XII, pp. 2 13-249 (1970, March)and Keay, L. and Moser, P. W., “Differentiation of Alkaline Proteasesform Bacillus Species” Biochemical and Biophysical Research Comm., Vol.34, No. 5, pp. 600-604, (1969).

The subtilisin enzymes are broken down into two sub-classes, subtilisinA and subtilisin B. In the subtilisin A grouping are enzymes derivedfrom such species are B. subtilis, B. Iicenifomiis and B. pumilis.Organisms in this sub-class produce little or not neutral protease oramylase. The subtilisin B. sub-class is made up of enzymes from suchorganisms a B. subtilis, B. subtilis var. amylosacchariticus, B.aniyloliquefaciens and B. subtilis NRRL B341 1. These organisms productneutral proteases and amylases on a level about comparable to theiralkaline protease production. One or more enzymes from the subtilisin Asub-class are particularly useful.

In addition other preferred enzymes are, for example, pancreatin,trypsin, collagenase, keratinase, carboxylase, aminopeptidase, elastase,and aspergillopeptidase A and B, pronase E (from S. griseus) and dispase(from Bacillus polymyxa).

An effective amount of enzyme is to be used in the practice of thisinvention. Such amount will be that amount which effects removal in areasonable time (for example overnight) of substantially all of at leastone type of debris from a lens due to normal wear. This standard isstated with reference to contact lens wearers with a history of normalpattern of lens debris accretion, not the very small group who may atone time or another have a significantly increased rate of debrisaccretion such that cleaning is recommended every day, or every two orthree days.

The amount of enzyme required to make an effective cleaner will dependon several factors, including the inherent activity of the enzyme, andthe extent of its interaction with the hydrogen peroxide present.

As a basic yardstick, the working solution should contain sufficientenzyme to provide about 0.001 to about 3 Anson units of activity,preferably about 0.01 to about I Anson units, per single lens treatment.Higher or lower amounts may be used. Enzyme activity is pH dependent sofor any given enzyme, there is a particular pH range that is mosteffective and the solution may be formulated to adjust the pH foroptimal enzyme activity.

EXAMPLE 1 Reduced Protein Deposition

Contact lenses were soaked and heated in test solutions to which aradio-labeled lysozyme was present in a known amount for a period of 12hours at 37 degrees Celsius. The lenses were rinsed with distilled waterin order to remove residual solution. The lenses were then assayed forprotein deposition using a Beckman BioGamma I counter. Results werereported in ug/lens.

LensA Lens B Average ug/lens ug/lens ug/lens Phosphate buffer control1,043 865 954 Choline Chloride (1%) in 14 9 12 phosphate buffer

Choline chloride was a 1 percent w/v solution. The matrix control wasphosphate buffer and sodium chloride. The low molecular weight aminesolution had lower protein binding than the control.

EXAMPLE 2 Reduced Preservative Binding

Contact lenses were soaked and heated in test solutions to which aradio-labeled C¹⁴-PHMB solution in a known concentration for a period of12 hours at 37 degrees Celsius. The lenses were rinsed with distilledwater in order to remove residual solution. The lenses were then assayedfor the radio-labeled protein deposition using a Beckman BioGamma 1counter. Results were reported in ug/lens.

Lens A Lens B Average Solution ug/lens ug/lens ug/lens 1% cholinechloride 18 11 14.5 in phosphate buffer 1% carnitine in 9 13 11phosphate buffer 1% betaine HCI in 6 8 7 phosphate buffer Phosphatebuffer 73 64 68.5 control

Each of the additives were at a 1 percent w/v solution in the phosphatebuffer. The control was phosphate buffer and sodium chloride. The lowmolecular weight amines solution had a lower cationic preservativeadsorption the control.

EXAMPLE 3A Example of Protein Deposition Inhibition

Contact lenses were soaked test solutions overnight. Afterwards,lysozyme was added to the tubes and warmed to 37 degrees Celsius for 12hours. The lenses were rinsed with distilled water in order to removeresidual solution. The lenses were assayed for protein deposition by theBCA method and detected on an HP PDA Spectrophotometer. Results werereported in ug/lens.

Solution ug lysozyme per lens Marketed Product Control >18.3 (phosphatebuffer, Poloxamer) Phosphate buffer control >26.16 Choline chloride (1%)4.1 Betaine HCI (1%) 2.44

Choline chloride and Betaine HCI were a 1 percent w/v solution in thephosphate buffer. The control was phosphate buffer and sodium chloride.The low molecular weight amine solution had lower protein binding thanthe control.

EXAMPLE 3B Improved Antimicrobical Activity

Formulations containing low molecular weight amines were prepared in a0.1% phosphate buffer. The solutions were made isotonic with sodiumchloride and preserved with polyhexamethylene biquanide at 0.0001% andhydrogen peroxide at 0.0060%. Dequest 2060S was added as a stabilizer.The pH was adjusted to 7.0 with either 1 N sodium hydroxide. The invitro microbicidal activity of the solutions was determined by exposingC. albicans to 10 ml of each solution at room temperature for 4 hours.Subsequently, an aliquot of each solution was serial diluted onto agarplates and incubated for 48 hours at elevated temperatures. At theconclusion of the incubation period the plates are examined for thedevelopment of colonies. The log reduction was determined based on acomparison to the inoculum control. The following table provides theresults of the in vitro studies.

C albicans log reduction Improvement bicine (1%) 0.75 0.34 creatinine(1%) 1.42 1.01 buffer control 0.41

Each of the low molecular weight amines showed an improvement in theactivity against C. albicans as compared to the buffer control.

EXAMPLE 4 Improved Antimicrobical Activity

Formulations containing exemplary low molecular weight amines wereprepared in a 0.2% phosphate buffer. The solutions were made isotonicwith sodium chloride and preserved with polyhexamethylene biquanide at0.0001%. The pH was adjusted to 7.2 with either 1N sodium hydroxide or 1N hydrochloric acid. The in vitro microbicidal activity of the solutionswas determined by exposing C. albicans to 10 ml of each solution at roomtemperature for 4 hours. Subsequently, an aliquot of each solution wasserial diluted onto agar plates and incubated for 48 hours at elevatedtemperatures. At the conclusion of the incubation period the plates areexamined for the development of colonies. The log reduction wasdetermined based on a comparison to the inoculum control. The followingtable provides the results of the in vitro studies.

C albicans log reduction Improvement betaine HCI (0.5%) 1.37 0.38bis-tris (0.5%) 1.21 0.22 carnitine (0.5%) 1.28 0.29 choline (0.5%) 2.241.25 creatine (0.5%) 1.72 0.73 tricine (0.5%) 1.33 0.34 triethylamine(0.5%) 1.64 0.65 triethanolamine (0.5%) 1.82 0.83 buffer control 0.99

Each of the low molecular weight amines showed an improvement in theactivity against C. albicans as compared to the buffer control.

EXAMPLE 5

An example of a preferred disinfecting formulation of the subjectinvention is provided below in Table I. This solution is prepared byweighing out the necessary amount of the tricine, creatine, cholinechloride, sodium chloride and edetate disodium into a vessel containingapproximately 90% of the water volume. After each of the ingredients hasdissolved, the pH is adjusted to 7.3 with either 1 N sodium hydroxide or1 N hydrochloric acid. Following this, the polyhexamethylene biguanideis added and the solution is brought to final volume with purifiedwater. The final product has the composition shown in the Table below.

TABLE 4 Constituent Weight/Volume Polyhexamethylenebiguanide 20% w/wsolution 0.0001%   HCI available under the mark Cosmocil CQ from AveciaTricine 1.0% Creatine 0.25%  Choline Chloride 0.5% Edetate Disodium0.055%  Polyoxyl 40 Hydrogenated Cremophor 0.1% Castor Oil RH 40 fromBASF Co. Sodium Chloride As required for tonicity adjustment 300 mOsmHydrochloride Acid, 1N as required for pH adjustment to 7.3 SodiumHydroxide, 1N as required for pH adjustment to 7.3 Purified WaterBalance to 100%

This solution may be used to rinse, clean, and store contact lenses on adaily basis.

EXAMPLE 6

An example of a preferred formulation for a contact lens vial storage ofthe subject invention is provided below in Table I. This solution isprepared by weighing out the necessary amount of the tricine, creatine,choline chloride, and sodium chloride into a vessel containingapproximately 90% of the water volume. After each of the ingredients hasdissolved, the pH is adjusted to 7.3 with either I N sodium hydroxide orI N hydrochloric acid. Following this, the polyhexamethylene biguanideis added and the solution is brought to final volume with purifiedwater. The final product had the composition shown in Table I below.

TABLE 4 Constituent Weight/Volume Tricine 1.0% Creatine 0.25%  CholineChloride 0.5% Polyoxyl 40 Hydrogenated Cremophor RH 40 0.1% Castor Oilfrom BASF Co. Sodium Chloride As required for tonicity adjustment 300mOsm Hydrochloride Acid, 1N as required for pH adjustment to 7.3 SodiumHydroxide, 1N as required for pH adjustment to 7.3 Purified WaterBalance to 100%

An example from another patent: specific representative embodiments ofbiguanides for use in the contact lens disinfectant methods include freebases and water soluble salts wherein:

EXAMPLE 7 Cleaning and Disinfecting Formulation

An example of a preferred cleaning and disinfecting formulation of thesubject invention is provided. This solution is prepared by weighing outthe necessary amount of the tricine, creatine, choline chloride, sodiumchloride and edetate disodium into a vessel containing approximately 90%of the water volume. After each of the ingredients has dissolved, the pHis adjusted to 7.3 with either 1 N sodium hydroxide or 1 N hydrochloricacid. Following this, the polyhexamethylene biguanide is added and thesolution is brought to final volume with purified water. The finalproduct has the composition shown in the following table.

Constituent % Weight/Volume Amount Purified water    40 mL Tricine 1.0% 0.500 g Creatine 0.25%   0.125 g Choline Chloride 0.5%  0.250 g EdetateDisodium 0.055%  0.0275 g Polyoxyl 40 Hydrogenated 0.1%   0.5 mL of 10%Castor Oil (Cremophor RH 40 from BASF Co.) Polyhexamethylenebiguanide0.0001%      50 uL of 0.1% HCI (20% w/w solution available under themark Cosmocil CQ from Avecia) Sodium Chloride As required for Asrequired for tonicity adjustment tonicity adjustment 300 mOsm 300 mOsmHydrochloride Acid, 1N as required for pH as required for pH adjustmentto 7.3 adjustment to 7.3 Sodium Hydroxide, 1N as required for pH asrequired for pH adjustment to 7.3 adjustment to 7.3 Purified WaterBalance to 100% Dilute to 50 mL

This solution may be used to rinse, clean, and store contact lenses on adaily basis.

EXAMPLE 8 Lens Vial Storage

An example of a preferred formulation for a contact lens vial storage ofthe subject invention is provided. This solution is prepared by weighingout the necessary amount of the tricine, creatine, choline chloride, andsodium chloride into a vessel containing approximately 90% of the watervolume. After each of the ingredients has dissolved, the pH is adjustedto 7.3 with either 1 N sodium hydroxide or 1 N hydrochloric acid.Following this, the polyhexamethylene biguanide is added and thesolution is brought to final volume with purified water. The finalproduct had the composition shown in Table I below.

Constituent % Weight/Volume Amount Purified water   40 mL Tricine 1.0%0.500 g Bis-Tris 0.25%  0.125 g Polyoxyl 40 Hydrogenated 0.1%  0.5 mL of10% Castor Oil (Cremophor RH 40 from BASF Co.) Sodium Chloride Asrequired for As required for tonicity adjustment tonicity adjustment 300mOsm 300 mOsm Hydrochloride Acid, 1N as required for pH as required forpH adjustment to 7.3 adjustment to 7.3 Sodium Hydroxide, 1N as requiredfor pH as required for pH adjustment to 7.3 adjustment to 7.3 PurifiedWater Balance to 100% Dilute to 50 mL

EXAMPLE 9 Disinfecting Solution

Formulation was prepared by dissolving Tricine, Carnitine, Betaine HCl,Choline Chloride, Inositol, Disodium edetate, and Cremophor RH40 in 80%of the water volume. The pH of the solution was adjust to 7.3 with 1 Nsodium hydroxide. The tonicity of the solution was adjusted with sodiumchloride and polyhexamethylene biguanide. The solution was diluted tovolume with water.

Constituent Supplier % Weight/Volume Amount Purified water to 80%    40mL Tricine Spectrum 1.0%  0.500 g Carnitine Spectrum 0.25%   0.125 gBetaine HCl Spectrum 0.1%  0.050 g Choline Chloride Amresco 0.5%  0.250g Inosito Spectrum 0.1%  0.050 g Edetate Disodium Spectrum 0.055% 0.0275 g Polyoxyl 40 Cremophor RH 40 0.1%   0.5 mL of 10% HydrogenatedCastor from BASF Co. Oil Sodium Hydroxide, 1N as required for asrequired for pH pH adjustment adjustment to 7.3 to 7.3 Purified Water to98% Dilute to 49 mL Sodium Chloride Fisher As required for As requiredfor tonicity tonicity adjustment 300 adjustment 300 mOsm mOsmPolyhexamethylene- 20% w/w solution 0.0001%      50 uL of 0.1% biguanideHCI available under the mark Cosmocil CQ from Avecia Purified WaterBalance to Dilute to 50 mL 100%

EXAMPLE 10 Lens Storage Solution (BCL1O6-037-3)

Formulation was prepared by dissolving Tricine, Camitine, and Inositolin 80% of the water volume. The pH of the solution was adjust to 7.3with 1 N sodium hydroxide and Cremophor RH40 was added. The tonicity ofthe solution was adjusted with sodium chloride. The solution was dilutedto volume with water.

% Weight/ Constituent Supplier Volume Amount Purified water to 80%  40mL Tricine Spectrum  1.0% 0.500 g Carnitine Spectrum 0.25% 0.125 gInositol Spectrum  0.1% 0.050 g Hydrochloride as required for asrequired for Acid, 1N pH adjustment pH adjustment to 7.3 to 7.3 Sodiumas required for as required for Hydroxide, 1N pH adjustment pHadjustment to 7.3 to 7.3 Polyoxyl 40 Cremophor  0.1% 0.5 mL of 10%Hydrogenated RH 40 from Castor Oil BASF Co. Purified Water to 98% Diluteto 49 mL Sodium Fisher As required for As required for Chloride tonicitytonicity adjustment 300 adjustment 300 mOsm mOsm Purified Water to 100%Dilute to 50 mL

What is claimed is:
 1. An ophthalmic solution comprising: 0.001 to about 5 weight percent of carnitine; an effective amount of biologically compatible buffer to maintain the pH of the solution between 5.5 and 8.5 pH; and the balance water.
 2. The ophthalmic solution of claim 1, further comprising an effective amount of a tonicity agent.
 3. The ophthalmic solution of claim 1, wherein the ophthalmic solution consists essentially of the carnitine, the biologically compatible buffer, an effective amount of a tonicity agent, and the balance water.
 4. The ophthalmic solution of claim 1, wherein the ophthalmic solution consists essentially of the carnitine, the biologically compatible buffer, an effective amount of a tonicity agent, and a preservative and the balance water.
 5. The ophthalmic solution of claim 4, wherein the preservative is poly[dimethylimino-2-butene-1,4-diyl]chloride, alpha[4-tris(2-hydroethyl)ammonium-dichloride. 